(1) Field of the Invention
This invention relates to a support frame of a cathode-ray tube for color television including a support frame member for supporting a shadow mask and an electron shield member formed integrally with each other, and more particularly it is concerned with improvements in or relating to an outer electron shield section.
(2) Description of the Prior Art
A cathode-ray tube for color television equipped with this type of support frame is disclosed in U.S. Ser. No. 921,953 dated July 5, 1978 (Japanese patent application Laid-Open No. 130280/77 now abandoned. The construction disclosed therein is such that a shadow mask located on an inner surface of a panel is supported on an inner surface of a panel skirt through a spring. The shadow mask is reinforced as it is affixed to the support frame serving concurrently as an electron shield. The support frame comprises an inner electron shield section, a mask fixing section and an outer electron shield section. The arrangement whereby the support frame is formed with the inner and outer electron shield sections as a unit enables its strength to be increased. Thus the support frame formed of soft steel can have its thickness reduced to about 0.15-0.8 mm.
Meanwhile it is necessary that the support frame have its cross-sectional length increased as much as possible, and a side wall portion of the outer electron shield section extending along the panel skirt preferably has its length increased as much as possible so as to effectively provide a shield to an electron beam entering from outside the shadow mask. However, the position of the shadow mask may vary depending on the relation between the pitch of a triplet of red, green and blue stripes of a fluorescent screen and the pitch of an array of electron guns. If the side wall portion of the outer electron shield section sticks out of a panel seal surface, then difficulties are experienced in the production of cathode-ray tubes for color television. In view of these factors, it is impossible to lengthen the side wall portion sufficiently to effectively shield the electron beam. Particularly in a type of panel of low panel skirt, the length of the side wall portion becomes very small and it becomes impossible to effectively shield the electron beam while the rigidity of the support frame is reduced.